I teach a course on injury prevention for graduate students. Early
in the course, I engage the class in a little exercise (shamelessly
borrowed from a colleague). First I ask all of the students to
stand. Then I tell them to remain standing if they wore their
seatbelt the last time they were in a car. Seat belt use rates are
about 85 percent nationally; nearly all the students remain
standing. Next I tell them to remain standing if they have a smoke
alarm in their home or apartment. Again, almost all are still
Then I ask about carbon monoxide (CO) detectors in the home. With a
loud thud, a large group of (relieved) students slump into their
chairs. Why the difference?
Is it because carbon monoxide is not really dangerous?
No. Carbon monoxide is an odorless, colorless gas caused by
incomplete combustion of fuel, including cooking or heating fuel in
the home. Unintentional carbon monoxide poisoning, from sources
other than fires in buildings, kills more
than 400 people
each year and sends another 15,000 to the
Is it because there are major barriers to acquiring and installing
No. Carbon monoxide detectors are relatively inexpensive (typically
about $10 -$25), easy to install (many just plug into an electric
socket but also have a battery back-up), and effective ways to warn
residents about a dangerous build-up of CO.
Is it that the students don’t know they should have a CO
No. When I ask, it’s clear that all (or nearly all) of the
students were aware that CO detectors exist and that they would
lower risk of injury, but many had still not acquired them. One
goal of the classroom exercise is to show the students that
knowledge about injury risks and countermeasures may be necessary
for action but, by itself, is often insufficient.
This is where the law can be an enormously important tool for
injury prevention. Many states and localities have laws
mandating smoke alarms
in residential buildings.
But not as many require carbon monoxide detectors. Just as
importantly, for almost any law to be successful, it must be
effectively publicized and enforced. And we’ve had a many year
head start publicizing the need for smoke alarms.
The law can also provide information about social norms –
attitudes and behaviors expected of a reasonable citizen – in
this case, whether to have a CO or smoke alarm. One day, when most
of my students remain standing when asked about CO detectors,
I’ll know that that the norm (and their risk of injury) has
changed.This information was developed by Jon S. Vernick, associate
professor at the Johns Hopkins Bloomberg School of Public Health;
deputy director of the Johns Hopkins Center for Injury Research and
Policy; and partner of the Network for Public Health Law – Eastern
Region.The Network for Public Health Law provides information and
technical assistance on issues related to public health. The legal
information and assistance provided in this document does not
constitute legal advice or legal representation. For legal advice,
readers should consult a lawyer in their state.